This invention relates generally to gas turbine engines, and, more specifically, a blade assembly for a gas turbine engine.
Some known turbines include a compressor that compresses fluid and channels the compressed fluid towards a turbine wherein energy is extracted from the fluid flow. Some known compressors include a row of blades secured to the compressor casing. Such blades may be secured to the casing using flanges on the base of the blade that are inserted into grooves defined in the casing. More specifically, in at least some known embodiments, the casing includes T-shaped grooves for each row of blades, and the blade flanges are sized and shaped to fit within the T-shaped groove.
During operation, some blades in the compressor may loosen in the grooves and shift with respect to each other and with respect to the compressor casing. Such movement may increase the turbine dynamics and may increase the wear of the blade. The movement of the blades may also induce stresses to the blade, which, over time, cause cracking or failure of the blade.
To reduce blade movement, some known compressor blades are shimmed to decrease the clearance between turbine blade bases and to limit movement of the blade within the casing. Some known shims are formed with tabs extending from each side to enable the shim to be secured in position against the casing. In at least some compressors, the tabs fit into the same grooves used to retain the blades within the casing. During turbine operation, some known shims may be chafed by the adjacent blade bases causing the shim to thin. As the shim wears, the clearance defined between the blade and the shim, or between the blade and the groove, is increased. Over time, the increased clearance enables the blades to move within the casing groove.
In some known turbines, during turbine operation, the pressure and loading on each blade and shim may fluctuate. Variations in loading induced to the blades and/or shims may cause wear of the shim tabs. Over time, the wear to the tabs may loosen the shim from the casing such that the shim may protrude into the fluid flow path and/or fall into the flow stream. Any shim protruding into the flow stream may disrupt the flow stream and/or decrease turbine operating efficiency. Any shim falling into the flow stream may contact other compressor components, such as the blades, which may damage such components.